1. Field of the Invention
This invention relates generally to integrated circuit (IC) devices or semiconductor devices. More particularly, the invention pertains to heat spreading apparatus and methods for dissipating heat from integrated circuit devices or semiconductor devices.
2. State of the Art
Integrated circuit devices (ICs) or semiconductor devices are devices including small electronic circuits formed on the surface of a wafer of semiconductor material, such as silicon. The ICs or semiconductor devices are fabricated in a plurality on the surface or as part of a wafer. The wafer is then subdivided into discrete IC or semiconductor device chips or dice, and then further tested and assembled for customer use through various well-known individual die testing and packaging techniques, including lead frame packaging, Chip-On-Board (COB) packaging, and flip-chip packaging (FCP). Depending upon the size of the IC or semiconductor device and the size of the wafer, a wafer may be divided into a few dice or as many as several hundred or more than one thousand discrete dice. The discrete IC or semiconductor device may be subsequently packaged in a variety of manners using lead frames, substrates, etc.
Higher powered, faster integrated circuits and/or semiconductor devices generate heat which, if not dissipated, may overheat the IC and/or semiconductor device, resulting in its failure.
Various means for dissipating heat from ICs and semiconductor devices have been used or proposed. Heat transfer through the metallic leadframe or other conducting wire has been enhanced in different ways, as shown in U.S. Pat. No. 5,541,446 of Kierse, U.S. Pat. No. 4,961,107 of Geist et al., U.S. Pat. No. 5,101,465 of Murphy, U.S. Pat. No. 4,264,917 of Ugon, and U.S. Pat. No. 5,656,857 of Kishita.
U.S. Pat. No. 5,450,283 of Lin et al. discloses a device in which the die surface is left unencapsulated in the packaging step for improved heat dissipation.
Use of an encapsulant composition having enhanced heat conducting properties is shown in U.S. Pat. No. 4,358,552 of Shinohara et al., U.S. Pat. No. 4,507,675 of Fujii et al., U.S. Pat. No. 4,931,852 of Brown et al., and Japanese Patent Application No. 58-202429 of Tanaka. U.S. Pat. No. 5,379,186 of Gold et al. discloses a package comprising inner and outer layers of encapsulant with an intermediate layer of thermally conductive material.
A die support member to which the die is adhesively attached has been used as a heat sink in a variety of configurations. Examples of such are shown in U.S. Pat. No. 5,701,034 of Marrs, U.S. Pat. No. 5,379,187 of Lee et al., U.S. Pat. No. 5,594,282 of Otsuki, U.S. Pat. No. 5,596,231 of Combs, U.S. Pat. No. 5,598,034 of Wakefield, U.S. Pat. No. 4,642,671 of Rohsler et al., U.S. Pat. No. 5,434,105 of Liou, U.S. Pat. No. 5,488,254 of Nishimura et al., U.S. Pat. No. 5,659,952 of Kovac et al., and U.S. Pat. No. 5,489,801 of Blish II.
A single plate of metallic material has been applied to the outside of the package as a heat sink. Such is shown in U.S. Pat. No. 5,552,635 of Kim et al., U.S. Pat. No. 5,173,764 of Higgins III, and U.S. Pat. No. 4,024,570 of Hartmann et al.
In U.S. Pat. Nos. 5,378,924 and 5,387,554 of Liang, a layer of thermal grease is inserted between the die and a heat sink.
U.S. Pat. No. 5,144,747 of Eichelberger, U.S. Pat. No. 5,311,060 of Rostoker et al., and U.S. Pat. No. 5,641,997 of Ohta et al. show IC devices with separate heat sinks within the encapsulant near a wall thereof.
U.S. Pat. No. 4,323,914 of Berndlmaier et al. teaches a heat transfer structure comprising a pool of liquid metal adjacent a parylene-covered die in a semiconductor device.
Various patents show the use of flat and non-flat metal conductors for reducing power-ground loop inductance and increasing capacitance to reduce noise and increase operational speed. See, for example, U.S. Pat. No. 5,214,845 of King et al., U.S. Pat. No. 5,559,306 of Mahulikar, U.S. Pat. No. 5,233,220 of Lamson et al., U.S. Pat. No. 5,436,203 of Lin, and Japanese Patent Application No. 60-178651 of Uno. None of these documents mention heat dissipation.
The various methods of heat dissipation require, in general, complex structures. Routes for moisture leakage into the package result from heat spreaders/sinks that are partially exposed. A new heat spreader construction is needed for producing an integrated circuit device with high heat removal rates and protection against electronic noise and spikes, all at low cost and minimum time expenditure, and without problems of leakage.